Sagot :
a) A(x) = =(x+2)^2-4^2=(x+2+4)(x+2-4)=(x+6)(x-2)
tu fais un tableau de signes
==> (A(x)<0 si -6<x<2
c)A(x)=x(x-2)
tableau de signes==> A(x)<0 si 0<x<2
d) A(x) = =(x+1)(1-x)
A(x)>0 si -1<x<1
b) A(x) = =
3x^2+11x+9=3(x^2+(11/3)x+3)=3[(x+(11/6))^2-(121/36)+3]=3[(x+(11/6))-13/36]
3[(x+11/6-(√13)/6)((x+11/6+(√13)/6))
A(x)<0 si-(11+√13)/6<x<-(11-√13)/6